c - When doing `char first_word[MAX_LENGTH + 1] = "test";`, is first_word a pointer or a string? -


this question has answer here:

i have code:

char first_word[max_length + 1] = "test"; printf("word input: %s\n", first_word); printf("word input: %p\n", first_word);

it prints both (prints string "test" , address).

in code, this:

char *arr_of_strings[max_length + 1]; arr_of_strings[0] = first_word;

and sets arr_of_strings[0] whatever first_word (which in case pointer because *arr_of_strings array of pointers, right?). when do

printf("arr @ 0 is: %s\n", arr_of_strings[0]);

it prints string again, can can print address so:

printf("arr @ 0 is: %p\n", arr_of_strings[0]);

so when c use first_word string , when use pointer?

the correct answer an identifier array of characters.

  • it's not string, because string isn't type in c. string in c defined sequence of characters including 1 0 / '\0' character @ end (indicating end). so, first_word can hold string, can't is string. can hold sequence of char, not strings.

  • it's not pointer, although evaluates pointer in contexts. except when used sizeof, _alignof or &, identifier of array evaluated pointer it's first element. so, first_word have type char * (a pointer type) in many contexts, e.g. assign pointer char *foo = first_word. still, evaluating pointer doesn't mean is pointer. operators sizeof, _alignof , & evaluate different results when used on array vs. used on pointer.

regarding question printf: %s in printf requires pointer char (char *) passed , expects pointer point string. hope understand means after reading explanation above.


Comments

Post a Comment

Popular posts from this blog

android - InAppBilling registering BroadcastReceiver in AndroidManifest -

i'm implementing inapp billing in android app. works well, however, i'm trying decouple broadcast receiver activity manifest. suggestion in android's trivialdrive sample: // important: dynamically register broadcast messages updated purchases. // register receiver here instead of <receiver> in manifest // because call getpurchases() @ startup, therefore can ignore // broadcasts sent while app isn't running. // note: registering listener in activity bad idea, done here // because sample. regardless, receiver must registered after // iabhelper setup, before first call getpurchases(). currently there's class extends broadcastreceiver : public class iabbroadcastreceiver extends broadcastreceiver { /** * intent action receiver should filter for. */ public static final string action = "com.android.vending.billing.purchases_updated"; private final iabbroadcastlistener mlistener; public iabbroadcastreceiver(iabbroadcastlistener listener) { m
Read more

python Tkinter Capturing keyboard events save as one single string -

is possible store keyboard events 1 string? code below stores 1 char , prints it. card reader or bar code reader, contains collection of character/ string not 1 character @ time. goal save char pressed text variable. from tkinter import * root = tk() def key(event): text= event.char text+= event.char print ("pressed", text) def callback(event): frame.focus_set() print ("clicked at", event.x, event.y) frame = frame(root, width=100, height=100) frame.bind("<key>", key) frame.bind("<button-1>", callback) frame.pack() root.mainloop() currently, creating text variable , everytime key() function gets called, , text stores last character typed. you can define text module level variable , , use module level text inside key function - text = '' def key(event): global text text+= event.char print("pressed", text)
Read more

sql server - Why does Linq-to-SQL add unnecessary COUNT()? -

here tables: create table customer ( cid int primary key, name varchar(32) ) create table ord ( oid int primary key, cid int foreign key references customer, address varchar(20) ) here's linq-to-sql statement: var aaa = c in db.customer select new { c, o = c.ord.tolist() }; and here's inexplicable query generated linq-to-sql: select [t0].[cid] [cid], [t0].[name] [name], [t1].[oid] [oid], [t1].[cid] [cid2], [t1].[address] [address], (select count(*) [dbo].[ord] [t2] [t2].[cid] = [t0].[cid]) [value] [dbo].[customer] [t0] left outer join [dbo].[ord] [t1] on [t1].[cid] = [t0].[cid] order [t0].[cid], [t1].[oid] i want understand how rid of count(*) part. it's entirely uncalled for! linq needs count(*) in order determine number of entries returned o = c.ord.tolist() .
Read more